Correlations of Crystal and Electronic Structure via NMR and X-ray Photoelectron Spectroscopies in the RETMAI(2) (RE = Sc, Y, La-Nd, Sm, Gd-Tm, Lu; TM = Ni, Pd, Pt) Series

Author(s)

Radzieowski, Mathis ^[1] ; Stegemann, Frank ^[1] ; Doerenkamp, Carsten ^[2] ; Matar, Samir F. ^[3] ; Eckert, Hellmut ^[2] ; Dosche, Carsten ^[4] ; Wittstock, Gunther ^[4] ; Janka, Oliver ^[1]

Affiliation

^[1] Univ Munster, Inst Anorgan & Analyt Chem, Corrensstr 30, D-48149 Munster - Germany

^[2] Univ Sao Paulo, Inst Fis, CP 369, BR-13566590 Sao Carlos, SP - Brazil

^[3] Lebanese German Univ, Sahel Alma Campus, POB 206, Jounieh - Lebanon

^[4] Carl von Ossietzky Univ Oldenburg, Inst Chem, D-26111 Oldenburg - Germany

• Document type: Journal article
• Source: Inorganic Chemistry; v. 58, n. 10, p. 7010-7025, MAY 20 2019.
• Web of Science Citations: 6

Abstract

A total of 35 intermetallic aluminum compounds have been synthesized from the elements via arc melting and characterized by powder X-ray diffraction. A total of 15 of them have been previously reported; however, detailed property investigations were missing. Compounds of the RETMAl2 (rare earth metal RE = Sc, Y, La-Nd, Sm, Gd-Tm, Lu) series with transition metal TM = Ni, Pd, and Pt crystallize isostructurally in the orthorhombic MgCuAl2 type structure (Cmcm, oC16, fc(2)). Single-crystal X-ray diffraction investigations were conducted on YNiAl2, LaNiAl2, YPdAl2, ScPtAl2, and YPtAl2. The TM and Al atoms form a {[}TMAl2](delta-) polyanion, the RE atoms reside in cavities within the framework. While the Sc, Y, La, and Lu compounds exhibit Pauli-paramagnetic behavior, consistent with all atoms being closed shell, the other RETMAl2 compounds show paramagnetism along with magnetic ordering at low temperatures, in line with an open-shell trivalent oxidation state for the RE atoms. Solid-state Al-27 NMR investigations were carried out on the Pauli-paramagnetic samples, all showing only a single central transition, in line with one crystallographic site for the respective atoms. The observed quadrupolar coupling constants and electric-field-gradient asymmetry parameters were found to be in good agreement with the density-functional-theory-calculated values. Isotropic resonance shifts are dominated by the Fermi-contact interactions with s-conduction electron densities at the Fermi edge (Knight shifts). The bonding characteristics mirror the electronic density of states and crystal chemistry of the family of intermetallic compounds under consideration. Both the Knight shifts and quadrupolar coupling constants can be predicted based on element-specific increments. (AU)

• FAPESP's process: 17/06649-0 - New Optical Materials based on Rare-Earth Doped Oxyfluoride Glasses and Ceramics: Structural Studies by Electron Paramagnetic Resonance Methods
• Grantee: Carsten Doerenkamp
• Support type: Scholarships in Brazil - Post-Doctorate